Update AlertState to use new APIs

[stephencelis]

Assuming the new APIs are locked-in, this updates our existing APIs to consume the new ones and not the deprecated old ones. In the process I introduced the ability to do 3+ buttons on alerts.

Some food for thought:

• Should ActionSheetState be renamed to ConfirmationDialogState? Pretty wordy...
• Or should it all be AlertState and we could introduce something like:

  enum AlertStateMode {
    case alert
    case confirmationDialog(titleVisibility: Visibility)
  }

[stephencelis]

This is breaking...but the rename seemed worth it to unify with Apple's APIs...

[iampatbrown]

withTransaction might not be needed here because self.transaction should already be applied to self.wrappedValue. It might even override other withTransaction/withAnimation calls higher up.
In the event you wanted to add support for .transaction()/.animation() to this binding, I've found the best way to maintain the animation precedence would be

extension Binding {
  func isPresent<Wrapped>() -> Binding<Bool> where Value == Wrapped? {
    .init(
      get: { self.wrappedValue != nil },
      set: { isPresent, transaction in
        guard !isPresent else { return }
        self.transaction(transaction).wrappedValue = nil
      }
    )
  }
}

[stephencelis]

Interesting! Good to know, thanks @iampatbrown!